I got this :
Check the latest stable kernel version from kernel.org
5.1.15
Get the kernel from kernel.org and this for the *stable* kernel
Using TMPDIR=/home/bhaskar/latest_kernel_build_Gentoo_2019-06-25/linux-tarball-verify.XwbUNj.untrusted
Making sure we have all the necessary keys
gpg: WARNING: unsafe ownership on homedir '/home/bhaskar/.gnupg'
pub rsa4096 2013-01-24 [SC]
B8868C80BA62A1FFFAF5FDA9632D3A06589DA6B1
uid [ unknown] Kernel.org checksum autosigner <autosigner@xxxxxxxxxx>
pub rsa4096 2011-09-23 [SC]
647F28654894E3BD457199BE38DBBDC86092693E
uid [ unknown] Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
uid [ unknown] Greg Kroah-Hartman (Linux kernel stable release signing key) <greg@xxxxxxxxx>
uid [ unknown] Greg Kroah-Hartman <gregkh@xxxxxxxxxx>
sub rsa4096 2011-09-23 [E]
pub rsa2048 2011-09-20 [SC]
ABAF11C65A2970B130ABE3C479BE3E4300411886
uid [ unknown] Linus Torvalds <torvalds@xxxxxxxxxx>
uid [ unknown] Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
sub rsa2048 2011-09-20 [E]
Downloading the checksums file for linux-5.1.15
Verifying the checksums file
gpgv: Signature made Sat Jun 22 15:01:21 2019 IST
gpgv: using RSA key 632D3A06589DA6B1
gpgv: Good signature from "Kernel.org checksum autosigner <autosigner@xxxxxxxxxx>"
Downloading the signature file for linux-5.1.15
Downloading the XZ tarball for linux-5.1.15
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 101M 100 101M 0 0 8237k 0 0:00:12 0:00:12 --:--:-- 8342k
Verifying checksum on linux-5.1.15.tar.xz
/usr/bin/sha256sum: /home/bhaskar/latest_kernel_build_Gentoo_2019-06-25/linux-tarball-verify.XwbUNj.untrusted/sha256sums.txt: no properly formatted SHA256 checksum lines found
FAILED to verify the downloaded tarball checksum
